Sm-Nd concentrations and Nd isotopes were investigated in the fine fraction of two Labrador Sea cores to reconstruct the deep circulation patterns through changes in sedimentary supply since the last glacial stage. Three sources are involved: the North American Shield, Palaeozoic rocks from northeastern Greenland, and mid-Atlantic volcanism. The variable input of these sources provides constraints on the relative sedimentary supply, in conjunction with inception of deep currents. During the last glacial stage a persistent but sluggish current occurred inside the Labrador Basin. An increasing discharge of volcanic material driven by the North East Atlantic Deep Water is documented since 14.3 kyr, signaling the setup of a modern-like deep circulation pattern throughout the Labrador, Irminger, and Iceland basins. During the last deglacial stage the isotopic record was punctually influenced by erosion processes related mainly to ice-sheet instabilities, especially 11.4, 10.2, and 9.2 kyr ago.

Model ages have been calculated relative to the present Depleted Mantle (147Sm/144Nd = 0.222, 143Nd/144Nd = 0.513114), assuming a one-stage, linear evolution for the Depleted Mantle (Ben Othman et al., 1984). Chondritic Undifferenciated Reservoir (CHUR) parameters are 147Sm/144Nd = 0.1967 (Jacobsen and Wasserburg, 1980), and 143Nd/144Nd = 0.512638 (Wasserburg et al., 1981). Errors on the 143Nd/144Nd ratios are given as 2 sigma. The accuracy of 147Sm/144Nd ratios is better than 2%. Measured Accelerator Mass Spectrometry (AMS) 14C ages (i.e., values in brackets) are normalized to PDB and corrected by -400 years for reservoir effect (Hillaire-Marcel et al., 1994). Ages reported for each sample depth were estimated by direct linear interpolation of available AMS14C ages (Hillaire-Marcel et al., 1994), assuming a constant sedimentation rate. Then these interpolated ages were calibrated using the curve of Stoner et al. (1998). Data for the surface sample 90-013- 017, for which age is estimated at 0, is taken from Innocent et al. (1997).

Supplement to: Fagel, Nathalie; Innocent, Christophe; Stevenson, Ross K; Hillaire-Marcel, Claude (1999): Deep circulation changes in the Labrador Sea since the Last Glacial Maximum: New constraints from Sm-Nd data on sediments. Paleoceanography, 14(6), 777-788